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#include <bitfield/bitfield.h>
#include <bitfield/8byte.h>
#include <stddef.h>
#include <limits.h>
#include <string.h>
#define EIGHTBYTE_BIT (8 * sizeof(uint64_t))
uint64_t bitmask(const uint8_t bit_count) {
return (((uint64_t)0x1) << bit_count) - 1;
}
static uint16_t bits_to_bytes(uint32_t bits) {
uint8_t byte_count = bits / CHAR_BIT;
if(bits % CHAR_BIT != 0) {
++byte_count;
}
return byte_count;
}
uint64_t get_bit_field(uint64_t source, const uint16_t startBit,
const uint16_t bit_count, bool big_endian) {
uint8_t result[8] = {0};
if(!big_endian) {
source = __builtin_bswap64(source);
}
copyBitsRightAligned((const uint8_t*)&source, sizeof(source), startBit,
bit_count, result, sizeof(result));
uint64_t int_result = 0;
if(!big_endian) {
// we need to swap the byte order of the array to get it into a
// uint64_t, but it's been right aligned so we have to be more careful
for(int i = 0; i < bits_to_bytes(bit_count); i++) {
int_result |= result[bits_to_bytes(bit_count) - i - 1] << (CHAR_BIT * i);
}
} else {
int_result = *(uint64_t*)result;
}
return int_result;
}
bool set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
const uint16_t bit_count) {
if(value > bitmask(bit_count)) {
return false;
}
int shiftDistance = EIGHTBYTE_BIT - offset - bit_count;
value <<= shiftDistance;
*destination &= ~(bitmask(bit_count) << shiftDistance);
*destination |= value;
return true;
}
uint8_t nth_byte(const uint64_t source, const uint16_t byte_index) {
return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
}
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